16 February 2018 Analysis of wavefront structures of diode lasers by their spatial and current dependent evolution
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Abstract
For nearly Gaussian beams the characterization of changes in the beam parameters with variation of the operating conditions using a Shack-Hartmann sensor is a well-known technique. For broad-area semiconductor lasers the beam analysis based on wavefront detection is still a field of high innovation potential for quality control since the wavefront gives an additional insight to the modal composition of the laser which is strongly influenced by the processes inside the resonator. The diode lasers used for investigation are based on the material system of GaAs (λ=808nm-980nm). They show a multimodal behavior strongly affected by thermal and electrical effects inside the active medium resulting in a complex structure of the intensity and wavefront pattern. The investigations in this paper have been carried out using a so called Gaussian telescope which allows a magnification of the beam cross section as well as the investigation of the spatial evolution of the intensity and wavefront distribution in vicinity to the beam waist. Furthermore the pattern of the detected wavefront is associated with Legendre polynomials to obtain a quantitative expression of the pattern. Additionally simulation software is used to connect the modal composition of the intensity with a set of Hermite Gaussian modes. The aim of our work is to combine these two tracks of information to find a way to forecast whether the laser under test shows a stable or instable intensity distribution over the whole operation current range.
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Inga-Maria Eichentopf, Inga-Maria Eichentopf, Martin Reufer, Martin Reufer, } "Analysis of wavefront structures of diode lasers by their spatial and current dependent evolution", Proc. SPIE 10518, Laser Resonators, Microresonators, and Beam Control XX, 105181J (16 February 2018); doi: 10.1117/12.2288324; https://doi.org/10.1117/12.2288324
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